Efficacy of Patient-Controlled Intravenous Analgesia with Esketamine for Herpes Zoster Associated with Breakthrough Pain

Background: Some patients with herpes zoster (HZ) experience an intermittent spontaneous, shortlived and severe pain, which is called breakthrough pain (BTP). The effect of analgesic drugs and invasive procedures is not significant. Therefore, treatment of HZ associated with BTP is challenging. Esketamine is a new N-methyl-D-aspartate receptor antagonist, with enhanced analgesic effects. This study aimed to evaluate the efficacy and adverse reactions of patient-controlled intravenous analgesia (PCIA) with low-dose esketamine for HZ associated with BTP. Objectives: To evaluate the efficacy and adverse reactions of PCIA with low-dose esketamine for HZ associated with BTP. Study Design: A retrospective, observational study. Setting: The study was carried out in the Pain Department of the Affiliated Hospital of Jiaxing University in Jiaxing, China. Methods: The clinical data of HZ associated with BTP treated by PCIA with low-dose esketamine at the Pain Department of the Affiliated Hospital of Jiaxing University, between October 2015 to October 2021, were collected retrospectively. The Numeric Rating Scale (NRS-11) scores of rest pain (RP) and BTP, frequency of BTP, Pittsburgh Sleep Quality Index (PSQI) score, and fasting blood glucose (FBG) were recorded and analyzed before treatment (T0) and on days one (T1) and 3 (T2), week one (T3), months one (T4), 3 (T5), and 6 (T6) after treatment. Adverse reactions during the treatment were recorded. Results: Twenty-five patients treated by PCIA with low-dose esketamine were included finally. Compared with T0, the NRS-11 scores of RP at T2, T3, T4, T5, and T6 decreased significantly (P < 0.05). The NRS-11 score of RP at T4 was significantly lower than that of T3 (P < 0.001), but there was no statistical difference between T5 and T4 (P > 0.05), the efficacy of esketamine in the treatment of RP was stable at one month after treatment. Likewise, compared with T0, the NRS-11 scores of BTP, frequency of BTP, and PSQI score decreased significantly at each time point after treatment (P < 0.05). These at T5 were significantly lower than T4 (P < 0.05), but there was no statistical difference between T6 and T5 (P > 0.05), the efficacy of esketamine was stable at 3 months after treatment. FBG also decreased significantly at each time point after treatment (P < 0.05), it tended to be normal and stable one month after treatment. All patients had mild symptoms of dizziness during treatment, and though a slight increase in noninvasive blood pressure (BP) was noted in all, the elevated BP did not exceed 30% of the baseline value. Four patients (16%) developed nausea without vomiting. There were no serious adverse reactions, such as respiratory depression. Limitations: The nonrandomized, single-center, small sample size, retrospective design is a major limitation of this study. Conclusions: PCIA with low-dose esketamine has a significant and long-term effect in the treatment of HZ associated with BTP. The RP was controlled, and the degree and frequency of BTP were significantly reduced after treatment, leading to improved quality of life. There were no serious adverse reactions worthy of clinical promotion.